Most languages have idioms and English has a large number, in the tens of thousands. They can present difficulties for language learners as they have a few strange characteristics. Firstly they are not literal. Secondly even if you know what each of the words in the idiom mean, it will not necessarily make any sense. Finally if you translate an English idiom back into your first language it will probably be nonsensical. Think about these three ideas with this English idiom. You will open a can of worms if you say that.